1 Acacia albicorticata. Polyad of subtype A1, in general view, showing the Y-shaped colpi on the central pollen grains. 2 Acacia macracantha. Polyad of subtype A1 in optical cross-section; the peripheral (arrowheads) and central (arrows) pollen grains are indicated. 3 Acacia caven. Polyad of subtype A2 in general view. 4, 5 Acacia atramentaria. 4, Equatorial view of three grains belonging to a polyad of type A1 showing proximal pori (arrowheads) and distal ora (arrows) on the free ends of the colpi. 5, Distal face of an isolated peripheric grain of a polyad of subtype A1 showing the H-shaped colpi. 6, 8 Acacia etilis. 6, Porate polyad of subtype B1, in general view, showing the angular position of the pori on the distal face of the central grains (arrow) and the suprareticulate exine. 8, Aspect of the distal face of two isolated peripheric grains. 7 Acacia cf. riparia. Polyad of subtype B1, in general transverse view showing the suprasubreticulate character of the exine (arrow). 9 Acacia magnibracteosa. Polyad of subtype B2; sector of a general view; on the distal face of the peripheral grains the subpseudocolpi (arrows) can be observed. 10 Acacia catharinensis. Polyad of subtype B2, sector of a general view; on the distal face of the peripheral grains the subpseudocolpi (arrows) can be observed. 11, 12 Acacia holtonii. 11, Polyad of subtype B3, general view of the bitetrad, showing the suprareticulate character of the exine and general disposition of the pollen grains. 12, Cross-section of the bitetrad, showing the disposition of the central and lateral grains in inner faces. 13 Acacia velutina. Isolated grain, in equatorial view, showing the distal and proximal pori and the optical cross-section of the exine.
Scanning electron photomicrographs. Figs. 1, 2, 5 - scale bar = 10 μm; figs. 3, 4, 6, 7 - scale bar = 5 μm.
1, 3 Acacia macracantha. 1, Polyad of subtype A1, in general view, showing detail of the shape of colpi on the central and peripherical grains. 3, Sector of the same polyad in reference to a central grain; note the triangular shape of the exine sector closest to the axis of symmetry (arrowhead), and the microgranulate, perforate surface of the exine (arrows). Double arrow marks the presence of an os. 2, 4 Acacia albicorticata. 2, Polyad of subtype A1 in general view. 4, Sector of central grains of the same polyad showing the quadrangular shape of the exine sector in contact with the axis of symmetry of the polyad (arrows) and the supramicrorrugulate surface of the exine. 5, 6 Acacia caven. 5, Polyad of subtype A2 in general view.6, Sector of a grain showing the exine surface with perforations placed within cavities of the tectum, and the microgranulate (arrow)exine of the colpi. 7 Acacia rigidula. Polyad of subtype A1; sector with two peripheral grains of the polyad with H-shaped colpi and densely perforate exine.
1 Acacia rigidula. Polyad subtype A1, section of the polyad comprising a periferal grain (p) and part of a central grain. On the distal face of the grains a drastic reduction of the ectexine towards the area of the colpi and their absence on these may be seen (arrows) . On the proximal face may be seen collumellar remains of the ectexine (arrowhead). The endexine, with a very irregular inner surface, is of even thickness in the whole of the grain, very often presenting an alveolar appearance. In tangential section the os is observed to form free lamellae (double arrows). Scale bar = 2.5 μm. 2 Acacia macracantha. Polyad of subtype A1, section of the polyad making up the peripheral (p) and central (c) grains. Note drastic changes in thickness of the ectexine. In the peripheral grains the foot layer is noticeably thicker than in the central grains. Scale bar = 2.5 μm.
1 Acacia monacantha. Polyad of subtype B2, section of the exine of the distal face of a central grain. Note the ectexine with a thin tectum and with perforations (arrowhead). Infratectal layer granular, bistratified, with the lower granular stratum formed by columellar-shaped granules fused at base forming the foot layer. At the level of the subpseudocolpi a modification of strata is evident on a zone parallel to the edge of the distal face (arrows). The left subpseudocolpus is marked by the sunken tectum. Scale bar = 1 μm. 2 Acacia cfr. riparia. Polyad subtype B1, section of the exine of the distal face of a peripheral grain, showing the perforations of the tectum and the strata of the infratectal layer, with the lower stratum formed by columellar-shaped granules fused at base into a discontinuous foot-layer. Scale bar = 500 nm. 3 Acacia cuspidata. Polyad of subtype B3, section of the exine of the distal face of a peripheral grain. Note the ectexine with strongly reduced, granular infratectal layer of lesser thickness than the endexine. Tectum wih superficial perforations. Over the exine Ubisch bodies making up the whole diameter of the lumina in the suprareticulum. Scale bar = 250 nm. 4 Acacia etilis. Polyad of subtype B1, section of the exine showing a reduced foot layer (arrowhead). Scale bar = 250 nm. 5 Acacia holtonii. Polyad of subtype B3 with exine characters similar to 3. Scale bar = 250 nm.